implemented and added test cases for DB dao. Added dependency of Hierarchical junit runner in parent pom

dao/pom.xml

@@ -44,6 +44,14 @@
       <groupId>log4j</groupId>
       <artifactId>log4j</artifactId>
     </dependency>
+    <dependency>
+        <groupId>com.h2database</groupId>
+        <artifactId>h2</artifactId>
+      </dependency>
+    <dependency>
+      <groupId>de.bechte.junit</groupId>
+      <artifactId>junit-hierarchicalcontextrunner</artifactId>
+    </dependency>
   </dependencies>
 
   <build>

dao/src/main/java/com/iluwatar/dao/DBCustomerDao.java

@@ -1,38 +1,130 @@
 package com.iluwatar.dao;
 
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.Consumer;
 import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
 
 public class DBCustomerDao implements CustomerDao {
 
+  private String dbUrl;
+
+  public DBCustomerDao(String dbUrl) {
+    this.dbUrl = dbUrl;
+  }
+
   @Override
   public Stream<Customer> getAll() {
-    // TODO Auto-generated method stub
+    
-    return null;
+    Connection connection;
+    try {
+      connection = getConnection();
+      PreparedStatement statement = connection.prepareStatement("SELECT * FROM CUSTOMERS");
+      ResultSet resultSet = statement.executeQuery();
+      return StreamSupport.stream(new Spliterators.AbstractSpliterator<Customer>(Long.MAX_VALUE, Spliterator.ORDERED) {
+        
+        @Override
+        public boolean tryAdvance(Consumer<? super Customer> action) {
+          try {
+            if (!resultSet.next()) {
+              return false;
+            }
+            action.accept(createCustomer(resultSet));
+            return true;
+          } catch (SQLException e) {
+            e.printStackTrace();
+            return false;
+          }
+          
+        }}, false).onClose(() -> mutedClose(connection));
+    } catch (SQLException e) {
+      e.printStackTrace();
+      return null;
+    }
+  }
+  
+  private void mutedClose(Connection connection) {
+    try {
+      connection.close();
+    } catch (SQLException e) {
+      e.printStackTrace();
+    }
+  }
+
+  private Customer createCustomer(ResultSet resultSet) throws SQLException {
+    return new Customer(resultSet.getInt("ID"), 
+        resultSet.getString("FNAME"), 
+        resultSet.getString("LNAME"));
   }
   
   @Override
   public Customer getById(int id) {
-    // TODO Auto-generated method stub
+    try (Connection connection = getConnection();
+        PreparedStatement statement = connection.prepareStatement("SELECT * FROM CUSTOMERS WHERE ID = ?")) {
+        statement.setInt(1, id);
+        ResultSet resultSet = statement.executeQuery();
+        if (resultSet.next()) {
+          return createCustomer(resultSet);
+        }
+    } catch (SQLException ex) {
+      ex.printStackTrace();
+    }
     return null;
   }
 
   @Override
   public boolean add(Customer customer) {
-    // TODO Auto-generated method stub
+    if (getById(customer.getId()) != null) {
-    return false;
+      return false;
+    }
+    
+    try (Connection connection = getConnection();
+        PreparedStatement statement = connection.prepareStatement("INSERT INTO CUSTOMERS VALUES (?,?,?)")) {
+      statement.setInt(1, customer.getId());
+      statement.setString(2, customer.getFirstName());
+      statement.setString(3, customer.getLastName());
+      statement.execute();
+      return true;
+    } catch (SQLException ex) {
+      ex.printStackTrace();
+      return false;
+    }
   }
 
   @Override
   public boolean update(Customer customer) {
-    // TODO Auto-generated method stub
+    try (Connection connection = getConnection();
-    return false;
+        PreparedStatement statement = connection.prepareStatement("UPDATE CUSTOMERS SET FNAME = ?, LNAME = ? WHERE ID = ?")) {
+      statement.setString(1, customer.getFirstName());
+      statement.setString(2, customer.getLastName());
+      statement.setInt(3, customer.getId());
+      return statement.executeUpdate() > 0;
+    } catch (SQLException ex) {
+      ex.printStackTrace();
+      return false;
+    }
   }
 
   @Override
   public boolean delete(Customer customer) {
-    // TODO Auto-generated method stub
+    try (Connection connection = getConnection();
-    return false;
+        PreparedStatement statement = connection.prepareStatement("DELETE FROM CUSTOMERS WHERE ID = ?")) {
+      statement.setInt(1, customer.getId());
+      return statement.executeUpdate() > 0;
+    } catch (SQLException ex) {
+      ex.printStackTrace();
+      return false;
+    }
   }
 
+  private Connection getConnection() throws SQLException {
+    return DriverManager.getConnection(dbUrl);
+  }
 
 }

dao/src/test/java/com/iluwatar/dao/DBCustomerDaoTest.java

@@ -0,0 +1,149 @@
+package com.iluwatar.dao;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeTrue;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.stream.Stream;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import de.bechte.junit.runners.context.HierarchicalContextRunner;
+
+@RunWith(HierarchicalContextRunner.class)
+public class DBCustomerDaoTest {
+  
+  private static final String DB_URL = "jdbc:h2:~/dao:customerdb";
+  private DBCustomerDao dao;
+  private Customer existingCustomer = new Customer(1, "Freddy", "Krueger");
+
+  @Before
+  public void createSchema() throws SQLException {
+    try (Connection connection = DriverManager.getConnection(DB_URL);
+        Statement statement = connection.createStatement()) {
+      statement.execute("CREATE TABLE CUSTOMERS (ID NUMBER, FNAME VARCHAR(100), LNAME VARCHAR(100))");
+    }
+  }
+  
+  @Before
+  public void setUp() {
+    dao = new DBCustomerDao(DB_URL);
+    boolean result = dao.add(existingCustomer);
+    assumeTrue(result);
+  }
+  
+  public class NonExistantCustomer {
+    
+    @Test
+    public void addingShouldResultInSuccess() {
+      try (Stream<Customer> allCustomers = dao.getAll()) {
+        assumeTrue(allCustomers.count() == 1);
+      }
+      
+      final Customer nonExistingCustomer = new Customer(2, "Robert", "Englund");
+      boolean result = dao.add(nonExistingCustomer);
+      assertTrue(result);
+      
+      assertCustomerCountIs(2);
+      assertEquals(nonExistingCustomer, dao.getById(nonExistingCustomer.getId()));
+    }
+    
+    @Test
+    public void deletionShouldBeFailureAndNotAffectExistingCustomers() {
+      final Customer nonExistingCustomer = new Customer(2, "Robert", "Englund");
+      boolean result = dao.delete(nonExistingCustomer);
+      
+      assertFalse(result);
+      assertCustomerCountIs(1);
+    }
+    
+    @Test
+    public void updationShouldBeFailureAndNotAffectExistingCustomers() {
+      final int nonExistingId = getNonExistingCustomerId();
+      final String newFirstname = "Douglas";
+      final String newLastname = "MacArthur";
+      final Customer customer = new Customer(nonExistingId, newFirstname, newLastname);
+      boolean result = dao.update(customer);
+      
+      assertFalse(result);
+      assertNull(dao.getById(nonExistingId));
+    }
+    
+    @Test
+    public void retrieveShouldReturnNull() {
+      assertNull(dao.getById(getNonExistingCustomerId()));
+    }
+    
+  }
+  
+  public class ExistingCustomer {
+    
+    @Test
+    public void addingShouldResultInFailureAndNotAffectExistingCustomers() {
+      Customer existingCustomer = new Customer(1, "Freddy", "Krueger");
+      
+      boolean result = dao.add(existingCustomer);
+      
+      assertFalse(result);
+      assertCustomerCountIs(1);
+      assertEquals(existingCustomer, dao.getById(existingCustomer.getId()));
+    }
+    
+    @Test
+    public void deletionShouldBeSuccessAndCustomerShouldBeNonAccessible() {
+      boolean result = dao.delete(existingCustomer);
+      
+      assertTrue(result);
+      assertCustomerCountIs(0);
+      assertNull(dao.getById(existingCustomer.getId()));
+    }
+    
+    @Test
+    public void updationShouldBeSuccessAndAccessingTheSameCustomerShouldReturnUpdatedInformation() {
+      final String newFirstname = "Bernard";
+      final String newLastname = "Montgomery";
+      final Customer customer = new Customer(existingCustomer.getId(), newFirstname, newLastname);
+      boolean result = dao.update(customer);
+      
+      assertTrue(result);
+      
+      final Customer cust = dao.getById(existingCustomer.getId());
+      assertEquals(newFirstname, cust.getFirstName());
+      assertEquals(newLastname, cust.getLastName());
+    }
+    
+  }
+
+  @After
+  public void deleteSchema() throws SQLException {
+    try (Connection connection = DriverManager.getConnection(DB_URL);
+        Statement statement = connection.createStatement()) {
+      statement.execute("DROP TABLE CUSTOMERS");
+    }
+  }
+  
+  private void assertCustomerCountIs(int count) {
+    try (Stream<Customer> allCustomers = dao.getAll()) {
+      assertTrue(allCustomers.count() == count);
+    }
+  }
+  
+
+  /**
+   * An arbitrary number which does not correspond to an active Customer id.
+   * 
+   * @return an int of a customer id which doesn't exist
+   */
+  private int getNonExistingCustomerId() {
+    return 999;
+  }
+}

pom.xml

@@ -50,6 +50,7 @@
  		<guava.version>19.0</guava.version>
 		<systemrules.version>1.15.1</systemrules.version>
 		<mockito.version>1.10.19</mockito.version>
+		<hierarchical-junit-runner-version>4.12.1</hierarchical-junit-runner-version>
 	</properties>
 	<modules>
 		<module>abstract-factory</module>
@@ -195,6 +196,12 @@
 				<version>${systemrules.version}</version>
 				<scope>test</scope>
 			</dependency>
+			<dependency>
+				<groupId>de.bechte.junit</groupId>
+  				<artifactId>junit-hierarchicalcontextrunner</artifactId>
+  				<version>${hierarchical-junit-runner-version}</version>
+  				<scope>test</scope>
+			</dependency>
 		</dependencies>
 	</dependencyManagement>